1. Field of the Invention
The present invention relates to vitamin B.sub.12 derivatives having enhanced hydrophobicity. The vitamin B.sub.12 derivatives are useful as a component of pharmaceutical compositions, foods, feeds and the like.
2. Related Art
As analogues of vitamin B.sub.12, cyanocobalamin, hydroxocobalamin, adenosylcobalamin, methylcobalamin and the like are known. However all of them are water soluble substances, and on an oral administration are taken up at a lower portion of the small intestine and a terminal portion at 50 cm of the ileum, by the action of an intrinsic factor in gastric fluid (VITAMIN SCIENCE II, physiological activities of vitamin B.sub.12, page 554, 1980, Tokyo Kagaku Dojin). Vitamin B.sub.12 is taken up by active transport, and vitamin B.sub.12 deficiency diseases are, in many cases, caused by a disorder of this uptake mechanism.
Since known vitamin B.sub.12 analogues are water soluble, their affinity for tissues is low, and in the case where the uptake mechanism is in disorder, they cannot be taken up by diffusion as an alternative uptake mechanism. Accordingly, it is desired to develop vitamin B.sub.12 derivatives which can be taken up by diffusion.
On the other hand, where vitamin B.sub.12 is added to a blended feed, it may be easily dissolved in water and removed. It is desired to develop hydrophobic vitamin B.sub.12 derivatives capable of exhibiting its native biological activities.